The present invention relates to antennas, and more particularly to an antenna configuration for a radar-based level measurement instrument or time of flight ranging system.
Time of flight ranging systems, are commonly used in level measurement applications, and are referred to as level measurement systems. Level measurement systems determine the distance to a reflector, i.e. reflective surface, by measuring how long after transmission of energy pulses or waves, an echo is received. Such systems typically utilize ultrasonic pulses, pulse radar signals, or microwave signals.
Pulse radar and microwave-based level measurement systems are preferred in applications where the atmosphere in the container is subject to large temperature changes, high humidity, dust and other types of conditions which can affect propagation. To provide a sufficient receive response, a high gain antenna is typically used. High gain usually translates into a large antenna size.
Two types of antenna designs are typically found in microwave-based level measurement systems: rod antennas and horn antennas. Rod antennas have a narrow and elongated configuration and are suitable for containers having small opening/flange sizes and sufficient height for accommodating the antenna. Horn antennas, on the other hand, are wider and shorter than rod antennas. Horn antennas are typically used in installations with space limitations, for example, vessels or containers which are shallow.
The level measurement instrument comprises a housing and a waveguide (i.e. the antenna). The level measurement instrument is mounted on top of a container or vessel and the antenna extends into the vessel. The level measurement instrument is typically bolted to a flange around the opening in the container. The housing holds the electronic circuitry. The antenna is coupled to the housing and extends into the vessel, and the antenna functions as a transducer and is excited by the circuitry to transmit electromagnetic energy pulses into the vessel, and receives the pulses that are reflected by the surface of the material contained in the vessel. To provide a good seal between the antenna and the flange opening o-rings and gaskets are employed. Typically, antenna configurations utilize o-rings or gasket internally to their assemblies to provide an antenna/vessel mounting configuration that is liquid tight.
It will be appreciated that the addition of o-rings and gaskets adds to the installation procedure. In addition, these components provide a potential failure point if not periodically inspected and replaced as necessary.
Accordingly, there remains a need for an antenna configuration for microwave or radar-based level measurement systems which overcomes these deficiencies.
The present invention provides an antenna configuration suitable for use in pulse radar or microwave-based time of flight ranging systems and level measurement instruments.
In a first aspect, the present invention provides an antenna structure suitable for use in a level measurement instrument for measuring the level of a material held in a container, the antenna structure comprises: (a) an upper section connected to the level measurement instrument, the upper section includes an installation thread which couples a matching thread portion on the container; (b) a lower section having an antenna, the antenna is responsive to the level measurement instrument for emitting electromagnetic energy pulses and receiving electromagnetic energy pulses reflected by the material held in the container.
In a further aspect, the present invention provides a level measurement system comprising: (a) a transducer for emitting electromagnetic energy and coupling reflected electromagnetic energy; (b) a controller having a receiver component and a transmitter component; (c) the transducer having an input port operatively coupled to the transmitter component and being responsive to the transmitter component for emitting the electromagnetic energy, and the transducer includes an output port operatively coupled to the receiver component for outputting reflected electromagnetic energy coupled by the transducer; (d) the receiver component converts the reflected electromagnetic energy into corresponding electrical signals, and the controller includes a program component for determining the distance travelled by the electromagnetic energy; and (e) the transducer includes an antenna assembly, the antenna assembly has an upper section for connecting to the level measurement instrument, the upper section includes an installation thread, and a lower section has an antenna, the antenna is responsive to the level measurement instrument for emitting electromagnetic energy pulses and receiving electromagnetic energy pulses reflected by a material held in a container.
In another aspect, the present invention provides a radar-based level measurement system for determining the level of a material contained in a container, and the system comprises: (a) a transducer for emitting radar pulses and coupling radar pulses reflected from the surface of the material; (b) a controller has a receiver component and a transmitter component; (c) the transducer has an input port operatively coupled to the transmitter component and responsive to the transmitter component for emitting the radar pulses, and the transducer includes an output port operatively coupled to the receiver component for outputting the reflected radar pulses coupled by the transducer; (d) the receiver component converts the reflected radar pulses into corresponding electrical signals, and the controller includes a program component for determining the distance travelled by the radar pulses; and (e) the transducer includes an antenna structure having an upper portion for connecting to the level measurement instrument, the upper portion includes a threaded section, the threaded section couples a threaded section in the container, and a lower portion has an antenna, the antenna is operatively coupled to the level measurement instrument to emit electromagnetic energy pulses and to receive electromagnetic energy pulses reflected by the material held in the container.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.